Sarcoidosis is a specific disease whose name is often mentioned in the House series. Almost in every patient with vague symptoms, House himself or one of his colleagues inevitably resorts to the remark "It may be sarcoidosis." What exactly is this mysterious disease?
The cause of the disease is not known. It affects people of younger age (usually about 40 years of age) who have certain genetic predisposition. The disease itself is possibly started by a banal viral infection that apparently irritates our immune system leading to its erratic response damaging our own tissues. From this point of view, we can consider sarcoidosis as a type of autoimmune disease.
Sometimes, sarcoidosis may be asymptomatic. The symptoms, when present, are related to affection of particular organs. Sarcoidosis can affect virtually any organ, but it most commonly attacks the lungs. The first sign is enlargement of deep lung lymph nodes. These lymphatic nodes are located so deep that they can not be palpated. The nodes can significantly enlarge and compress nearby lung tissues causing shortness of breath and dry cough. These symptoms are frequently accompanied with fever, general malaise and night sweats. Some types of sarcoidosis can progress into deposition of connective tissue within lungs – lung fibrosis.
Sarcoidosis can cause disorders in calcium metabolism associated with increased level of calcium in the blood (hypercalcemia). This situation occurs due to production of vitamin D-like substances by the inflammation causing increased calcium absorption in the intestines. High level of calcium can damage the kidneys and urinary tract as the crystals can form urinary stones. The greatest risk of high blood calcium level, however, lies in affecting the cardiac activity, which can lead to life-threatening arrhythmias. Hypercalcemia is also related to a higher incidence of peptic ulcers.
A major complication of sarcoidosis is eye inflammation that may damage the eyesight and turn the patient blind. The enlarged lymph nodes may occur practically anywhere including the subcutaneous tissues where they can be palpated. Some people may experience pain and rash on the skin, pain and inflammation in the joints, muscle pain and many other symptoms.
Affected pulmonary lymph nodes and lung tissue can be easily visualized by chest X-ray. The pulmonary form may be somewhat similar to tuberculosis, but the tuberculin skin test is negative. The diagnosis is best confirmed by a sample of the affected tissue (biopsy), which is examined under a microscope and proves the specific inflammatory process.
There is also a special examination known as the Kveim test. A special substance (that includes small sample of a spleen of a patient with already confirmed sarcoidosis) is injected under the skin of the examined patient. The positive result is a small local inflammatory reaction presenting as a subcutaneous nodule.
There is no effective prevention of sarcoidosis.
The disease has in general a good prognosis and in many cases it disappears spontaneously. The therapy focuses on more severe course of sarcoidosis and the drugs of choice are immunosuppressive medications such as the corticosteroids. However, these drugs have many side-effects when used regularly. Due to possible complications, the patients should undergo regular chest X-rays and blood tests including the examination of calcium blood level.